It not so much that it gets cold (the coldest months are Dec-April, with av nighttime temps of 10-12C), but that Maltese houses are built to keep cool in the summer not warm in the winter. This is less so with many apartments - flip side is that old houses require less aircon (if any) in the summer unlike many apartments
what I've seen in houses, people use one or more of
electric - airconditioner/heaters or floor standing heaters
kerosine - big tank on the roof, one large burner
wood - one large burner
gas - bottled
I'd say most use gas as the primary - its the cheapest (unless you have a cheap wood supply). Gas bottles are subsidised, having not really gone up in price over 6 years, whereas electricity is up 50% plus, kerosine up 4X (kerosine used to be very cheap, but bus drivers were using it instead of diesel so was repriced by govt). Occasionally there is a shortage of gas bottles (plus they are only delivered once a week), so most have a backup of an electric heater or two
Can anyone give me an idea what it costs to keep warm through the winter? - we use gas, and probably get through 30 cylinders during the winter (so a cost of Euro 300), but we have a biggish house with very high ceilings - friends of ours living in an apartment block use 5 a year